JACKSONVILLE, Fla. (CBS News/CBSLA) — A gunman killed three people, including himself, and wounded nine others when he opened fire Sunday at a Madden NFL 19 gaming tournament at a popular waterfront mall in Jacksonville. Graphic recordings from the scene captured gunshots ringing out and the screams of terrified patrons taking cover.

A heavy police presence remains into the night at the shooting inside Jacksonville Landing on Aug. 26, 2018 in Jacksonville, Fla. (Getty Images)

David Katz, 24, of Baltimore, Maryland, is believed to be the gunman, Jacksonville Sheriff Mike Williams said. Katz used a single handgun to carry out the shooting and died from a self-inflicted gunshot wound. Williams described Katz as a white male who was attending the gaming event. He did not know if Katz knew the victims.

Nine others were wounded by gunfire and two others were injured as they fled the shooting, Williams said. They are all in stable condition.

One of the murdered victims was identified as 22-year-old Elijah Clayton, a former student at Calabasas High School. The school’s football team tweeted its condolences Sunday evening. The other victim has been identified as 27-year-old Taylor Robertson of West Virginia.

Our hearts are broken as we learned that former Calabasas Football player @True__818 (Elijah Clayton) was senselessly murdered today during the mass shooting in Florida. We send our love, condolences, and deepest sense of sorrow to Elijah's Family and Friends pic.twitter.com/xhdQ8TLg0d

The tournament for “Madden NFL 19” players was being held at the GLHF Game Bar, which shares shares space with a restaurant. The bar told CBS News in a Facebook message that all staff members and the owner were able to escape “untouched.”

The suspected shooter was a one-time Madden tournament champion known by his gamer tag “Bread.”

Katz had lost in Sunday’s tournament against Dennis Alston.

“I beat him and I went to shake his hand to tell him good game and he just looked at me and didn’t say anything,” Alston said.

EA Sports lists Katz as a 2017 championship winner.

There were 150 people involved in the two-day event, including players and spectators. Players were competing for a chance to play in the final round in Las Vegas. “This is your chance to earn your spot in the first Major’s Live Finals happening in October 2018,” the Facebook page for the event reads. “Don’t hesitate to secure your spot!”

Tony Montagnino, a father of two who was competing in Sunday’s tournament, was shot in his lower back and leg.

“I could never see his face because all I could see was the flash from the muzzle of the gun,” Montagnino said.

“If you would have told me that I was going to get shot playing a video game, I would have called you a liar,” Montagnino added. He said when the shooting started, he immediately dropped to the floor.

“My phone is on the ledge, you know, probably about 10 feet in front of me. And all I can think about is getting my phone so I can text some of my family,” Montagnino said, choking up with emotion. “Just let them know, you know, that I care about them, and that’s the most helpless feeling in the world.”

When the shots first rang out, witnesses said they thought it was a firecracker or balloons popping. No one expected a shooter to turn up at a qualifying round for a video game tournament. Then panic set in and people were trampled rushing for the exits.

A livestream from the event shows what appears to be a red dot flash across one of the players’ chests seconds before the first shots ring out. One witness described the “pop pop pop” sounds that “didn’t stop.”

Gunshots can be heard in recordings from the tournament on the bar’s Twitch account, which was streaming the competition. Williams said investigators were reviewing the footage as evidence and encouraged the public to turn in any additional videos that could help with the investigation.

Williams said the FBI is assisting with the investigation in Baltimore. Investigators believe Katz may have stayed in a hotel during the event. Williams said authorities have impounded Katz’s vehicle and plan to search it for evidence.

Late Sunday night, the FBI said heavily armed agents had entered the family home of the suspect. Dave Fitz told The Associated Press that agents went to the upscale townhouse home of the man’s father in Baltimore, but didn’t release any further information, citing the ongoing investigation.

The AP reports that agents could be see inside the home near Baltimore’s Inner Harbor wearing bulletproof vests and carrying long guns. Reporters at the scene did not see any authorities carrying any bags of evidence outside.

FAST FACTS

A shooting broke out at a “Madden NFL 19” tournament

3 were killed, including the gunman

11 injured: 9 with gunshot wounds, 2 fleeing the scene

Suspect identified as David Katz, 24, from Baltimore, Maryland

A motive for the shooting wasn’t immediately clear

Drini Gjoka, who was competing in the event, tweeted about the shooting in the immediate aftermath. “The tourney just got shot up. Im leavinng [sic] and never coming back,” he wrote at 1:37 p.m. Four minutes later, he added that a bullet struck him in the thumb, and later called Sunday the “worst day of my life.”

“I will never take anything for granted ever again. Life can be cut short in a second,” he said.

Florida Gov. Rick Scott, who was traveling to Jacksonville, tweeted that he offered state resources to the local law enforcement. His office said the Florida Department of Law Enforcement and Florida Highway Patrol were assisting in the investigation.

EA Sports said it was aware of the shooting and is working with authorities to gather information. “This is a horrible situation, and our deepest sympathies go out to all involved,” the company said. “Our focus right now is on those affected, and supporting law enforcement as they continue their investigation into this crime.”

The NFL issued a statement saying it was “shocked and deeply saddened by the horrific tragedy” in Jacksonville. “We support our partners at EA Sports and will continue to monitor developments with local law enforcement.”

Democratic Leader Nancy Pelosi said in a statement Sunday, “Congress must stop stalling and act to protect Americans from the gun violence epidemic, and ensure no other family or community has to endure this unspeakable pain. Every day it fails to act is a stain on our nation.”